This invention relates to the field of road and bridge construction, and, more particularly, relates to the design of expansion joints for bridges and for other applications where the expansion and contraction of pavement sections must be accommodated.
In the past, various types of expansion joints have been devised such as those described in the following U.S. Pat. Nos. 3,830,583; 3,699,853 and 3,854,159. The expansion joints currently available typically provide for structual support members extending across the gap to be joined, generally at right angles thereto. This arrangement requires that a recess must be made in the ends of the pavement sections being joined sufficiently deep to accommodate the maximum anticipated travel or expansion in question. It would be desirable to eliminate the need for such a recess or to at least reduce it in size.
It is common to provide an expansion joint comprised of several rigid members or beams, the top surface of which serve as the road wearing surfaces, said beams being separated by resilient expansion seals. One of the difficulties with this type of design is that there is generally no means for equalizing the spacing between the beams with precision. One attempt at eequalizing this spacing and the resultant distribution of stress loading has been to utilize leaf springs as described in U.S. Pat. No. 3,830,583. Although this solution to the problem has been partially successful, it would be desirable to equalize the spacing and stress loading more precisely.
Another disadvantage of expansion joint designs presently in use concerns the method of anchoring the beams on their associated structual support members. Frequently, inadequate anchoring is used which permits too much vertical and rocking motion of the beam. As a result, many of these joints tend to produce loud slapping noises as vehicles and other traffic pass over them. Thus, it would be desirable to provide a method of holding the beams in their proper positions more effectively so that the expansion joint would be quieter in operation.
In modular expansion joints, the beams are usually separated by extruded resilient seals which must be replaced from time to time. These seals serve to provide lateral support to the beams thereby generally adding strength to the joint. They also protect the internal moving parts of the joint from the weather and dirt which would otherwise be free to enter the joint. The seals are generally kept in place by shoulders formed as part of each beam. One disadvantage of this arrangement is that it is very difficult to remove and replace the seals due to the need to force them around the shoulders. Thus, it would be desirable to provide a means for more easily removing and replacing these seals.
As with most types of construction involving structures supported by abutments, piers, pylons and the like, a certain amount of settling usually occurs in bridge or road construction. This involves changes in vertical and lateral alignment of the bridge sections to be joined which, of course, can adversely affect the performance of expansion joints. Thus, it is desirable to provide an expansion joint whose performance would not be adversely affected by subsequent misalignment due to the settling of the pavement or bridge sections being joined.